Heat exchanger



May 18, 1937. H. KUHNI HEAT EXCHANGE}? 2 Sheets-Sheet 1 Original Filed March 10, 1934 Ill Attorney Patented May 18, 1937 UNITED. "STATES PATENT oi-Pica W -2,os1.oas fl HEAT "EXCHANGER Hans KiihnL'Bascl, Switzerland, assignor to e lAir'Liquide, Societe Anonyme pour IEtllde & 1

lExploitation des Procedos Georges Claude,

Paris, France Application March 10, 1934, Serial No. 114,967.

Renewed October 12, 1936. In

.March 13, 1933 Great Britain -6 Claims. (01. 257-225) The present invention relates to a heat exchanger for fluids in which one. of theiiuids passes in parallel streams through the-tubes of concentric layers of helically wound tubes that are placed 'in a casing, whilst the other fluid passes through the casing outside the said tubes, for exam'ple, in the opposite direction to thefirst fiuid.- -It is known that it is advantageous to create in thefiuids eddies or whirls which favour the thermal exchange between them.

To this end in the exchanger according to the present invention the innermost layer is wound in one direction, say left-hand, and the next layer is wound in the opposite direction (right-;

hand), the third layer is wound in the same direction as the first and so on. The tubes of each layer touching those of the adjacent 'layers, or adjacent layer in the cases of the first and last layers, at the points of meeting' of their wind ing s, Asfor the innermost (central) layer No.1, it can be supported on a cylindrical core placed in the axis of the exchanger; nofluid. passes in side this core.

The ends of the tubes of the different layers are, as usual, fixed intube-'plates and may be arranged in .a circle for each layer.

The ends of the'tubes of layers No. 1 and No. 2 may also be fixed in the same circle and then the ends of the layers No. 3 and No. 4 in another common circle,- in which case the ends of the tubes of. the layer '1 alternate inplace on. the circle with'the ends;

of the tubes of the layer 2, similarly forlayers 3 and 4 and so on. I

The accompanying drawings show diagram- .of this half-turn being diagrammatically indicated on Figure 1 by an arrowed line.

matically and by way of example the principle of construction 01 a vertical exchanger accord-,

. ing to the present invention. Figure 2 is a plan view of a part ofthe lower terminal tube-plate, Figure 1 is a partial section on a plane passing throughthe line l-l of Figure 2, and Figure 3, is a transverse sectionof the exchanger at .the

f tube plate. Figs. 1 and 2 show only some of the tubes in the innermost circle of tubes.

A denotes the inner-core or axial tube the ends of the tubes are fixed. B (Figure 1) which connects the twoparallel tube-plates in which meets the tube 3 at Z and then meets the tube -l at Z", whilst the tube 4 meets the tube'l at" denotes the lower one of these plates, part oi which is shown by Figure 2. C indicates the common circle in which are fixed the ends of the .firstand secondof innermost layers. In' order s to facilitate the description, it will be supp sed that the first layer is composed only of two tubes 1 and 3 and the second layer similarly composed of two tubes 2. and 4 and there hasfonly been shown in Figure 1 the commencement of "of odd-tubes being wound on the external sur-' of a half turn, the projection of this half turn ,being shown on Figurel, the tube then passes 'thetubes l and 3 along other helices which are parallel to-eachother and are of thesame pitch the tubes as seen when, viewed from the front of the plane l-l, the exchanger is seen with the: core A partially removed. The course of each of thetubes is indicated by an arrowed line when it is in front of the plane ll; again, in-accord- 5 ance with a system of representationemployed in electricity for windings, the centre of each section of tube cut by the plane l'l has a point allotted to it when'the tube passes to the front 7 of the said plane, and by a cross allotted to it 10 when it passes behind the same plane. In Figure 2 there is indicated'only the first circle Cof the four tubes 1, 3-2, 4 and the horizontal projection of these tubes has beenshown only up to the first crossing of I with l and of 3 with 2. l 7

The construction of the exchanger is as follows: the tubes l and 3 forming the first (innermost) layer are coiled in the same direction around the core A so as to form two helices; the

winding is efiected, for example, as shown, from right to left (F igure 2). Thus the tube 3 rises out of the plate B, passes from the right tothe leftthat is beh'ind'the plane l-l -an d continues until it again cuts this plane at the-end in frontv of the plane. The tube I rises in the same way, but 'first-of all passes in front'of the plane l,l. and then returns to the back of this plane at the end of a half'turn theprojection The tubes [I and; being thus coiled and fixed, into the tube-plates the tubes 2 and 4 are mount ed by winding them': round thehelices formed by as the tubes land 3, but in the opposite'direction, so as to create round the, core A two superposed concentric crossing layers} of helicoidaltubes. Consequently, the tube 2 first of all Z and the tube 3 at 2"" and so, onuntil the top tube-plate is reached in'which the two tubes 2, are fixed.

Under these conditions, by arranging on the same circle C several series of -tubes.alternately odd I, 3) and even (2, 4) and disposing similarly on a larger circle 0', distant from circle "0' by double the diameter of a tube, further series of tubes alternately odd, and even, the. next series face'of tubes 2- 4 and the next series-of even tubes being wound on the external surface of the preceding odd tubes and so on, so that there are produced a number of helicoidallayers which are superposed one on the other but the helices of which are successively in theopposite sense to each other.

In the working of the exchanger the fluid pass ing along the external surface of the tubes'is divided by these numerous tubes placed close one to another into a plurality of streams which flow parallel to the two series of helices and which, at the points of contact of the tubes Z',

Z" and Z, 2" meet one another and thus ore-- vantageous to use a number of said tubes theratio of which, to the radius of the said circle, is-a constant for the successive circles. As previously noted, the meeting points of tubes have been given a reference character Z; such a meeting or contact point, for example Z, occurs for successive layers of tubes on a same line and at right angles to the central core axis (see line extended between points Z'Z in Fig. 2). Consequently, the tubes can be arranged to meet at definite points, to create eddies as defined before, these contacting areas being further supported by the central core to impart rigidity to the system. 7

The above will be illustrated on referring to Figure 3 wherein a horizontal section through the lower tubular plate of the exchanger is 'sche matically depicted. The exchanger shown comprises four superposed layers of tubes spirally wound; the reference character B showing the tube plate, A the tube constituting the central core, around which the first layer is wound, as

from the axis of the exchanger,'G is the outside casing orenvelope of the exchanger. The extremities of the tubes connected to the tube plate are distributed according to concentric circles C and C: the tubes I, 3, 5, I issue from the circle C and, upon winding on the; core A, constitute a first layer of spiral tubes wound from right to left when seen at the axis and as shown by the arrow of Figure 3. The tubes 2, I, i, I also .issue from circle C and winding over the first layer of tubes, constitute" a second layer thereof, the winding of which is in a reverse direction to that of the first layer, as-shown by the other arrow of Figure 3. A third layer of tube is constituted by tubes l', 3', 5', '1', 9', ll, starting from the circle 0' and thewinding is reverse to that of the tubes of the second layer and, finally, the fourth layer is constituted by the tubes 2', 4', e', 8', ll, I2, also issuing from.

circle C and wound in a direction reverse to that of the tube of the third layer. Thus, it will be .seen that the ratio'of the number of tubes on the circle C to the radius of this circle is equal to the ratio of the number of tubes on the circle C' to the radius of this-last circle.

On the other hand, it is advantageous to have all the lengths of the tubes from which the coils are formed as nearly equal as possible, so that:

the drop of pressure of the fluid passing through each tube will be nearly the same for all the tubes and that therefore thisfluid will pass in the same quantity through all the tubes; for this purpose 'the pitch-of the windings of the diftubes of the layer.

' radius of said tube ends ferent layers is so much the greater as the respective layer is far from the axis of the heat.

exchanger.

--A furtherimprovement to the-present heat exchanger is accomplished during its construc-.-

tion by 'pressingeach tube of each layer against the tubes ofthe next inner layer at the places where the said tube touches the tubes of the said layer, with a sufiicient strength as to force back at those places towards the interior of the tubethe metal of said tube which is for example made of copper more or less annealed,

By referring to the apparatus shown in the drawings, this can be executed at the time of winding a tube on a layer already in place, by pulling said tube towards the interior of the layer so as to crush more or less deeply the metal of the tube at the places where it touches the The driving or forcing back thus obtained of the metal at certain places of the tube results in lessening the section of said tube at. those places and this improves, as is well known, the transmission of heat between the fluid passing through the interior of the tube and the fluid passing over the exterior on account ofthe succession-of drops in pressure. which is produced in the flow of the mud in the tube.

The. present exchanger especially enables a very thorough exchange of heat to be obtained VEDOUIS.

between two fluids-e. g.,- between two gases or I claim: 5 1. In a heat exchanger a* casing, a

wound tubes arranged inside the casing in layers at the points of meeting of thei-r opposite wind-g 2. Heat exchanger according to claim 1, in

core concentrically mounted in said casing, helically which the innermost layer of tubes'is wound round a cylindricalcore through which no. fluid p 3. In a heat exchanger, a casing for one of.

the fluids, helically wound tubes-arranged inside the casing in concentric circles on tube. plates,

' the odd'tubes on eachcircle being wound in one direction and the even tubes on same circle being wound in the opposite direction, said tubes touching one another-at-the points of meeting of their opposite windings and similarly touching th tubes of the immediately next layers.

4. In apparatus. for heat exchange betwee fluids, a casing adapted to hold one fluid, and helically wound tubes disposed in concentric circles inside said casing and within which another .fiuid circulates in parallelstreams, odd tubes of each circle being wound in one direction while even tubes run in opposite directions, said tubes contacting at the meeting ..points of opposite windings and with .tubes of immediately next layers-the ratio of the number .of tubes to-t he circle is constant for all circles of tubes- 5. apparatus as claimed in claim 4, wherein the individual pitch of the tube windings varies in direct ratio to the spacing of each winding from the,axis of the casing.

6. Apparatus as claimed in claim 4, wherei the tubes are flattened .at the contacting points thereof;

HANS Kiimn. 

